Some new users might find that suddenly, they can’t browse anymore, and the error console states that myoldspec is not defined.
The bug is fixed in version 3.1.4, however a quick fix is to open about:config and add “http://www.google.com” (without quotes) to extensions.tbrowse.dropdown
If you are currently using version 3.1.3 and you clear your dropdown history, you will be unable to browse until you add a url to the above pref.
Somehow, the fix was not included into the final build of 3.1.3, it is now in 3.1.4.